This invention relates to stereo or three-dimensional cinematography and video, e.g. to moving pictures and television which have an apparent depth of field dimension when viewed on an appropriate screen or similar display. The invention is particularly concerned with a process and apparatus which allows viewing without need for the viewer to wear special lens or optical filters to observe the third dimension effect.
The essential principles of three-dimensional cinematography have been known and described in various patents and other literature for most of this century, but a practical, consistent and acceptable process and apparatus has yet to achieve more than fleeting commercial success. The parlor "stereopticon" was well known around the end of the 19th century, and applications of the same fundamental stereo optics are found in two U.S. patents, Cervenka U.S. Pat. No. 1,163,892 of 1915 which resulted from work evidently done in France around 1911, and Hahn U.S. Pat. No. 1,282,073 of 1918, which appears to have an Australian origin around 1917.
The '892 patent features a fixed mirror d mounted at forty-five degrees to the optical centerline of a moving carmera lens b, and a movable mirror e supported in slide tracks i and moved toward and away from mirror d by a lever j which is controlled by a rotating cam k. The effect is shown in FIG. 1 and the resulting placement of successive picture frames on the film is shown in FIG. 5. It is also suggested that the lens b can be shifted back and forth to produce the result.
The '073 patent uses a central oscillating reflector 8, which pivots on a vertical axis 9-10 in front of lens 11 between spaced apart and fixed secondary reflectors 6 and 7 which are mounted at opposite sides of the lens axis. Motion of the central reflector is controlled by a cam 24, follower 21, and links 14 and 17, which allow the central reflector 8 to pause at the limits of its motion. A similar arrangement, using continuously orbiting pairs of reflectors is disclosed in Feil U.S. Pat. No. 1,929,685, and in French Pat. No. 794,608 of Feb. 21, 1936.
Of more recent vintage, McElveen U.S. Pat. No. 4,303,316 of 1981 discloses a single or double camera system. In the former, opposite sides of a lens 32 are alternatively blocked by a reciprocating shutter mechanism outside the front of the lens system as shown in FIGS. 5a and 5b, and a similar effect is used in the two camera systems, FIG. 6. Essentially the same arrangement, using reciprocating or rotating orifice plates in front of the lens, is disclosed in French Pat. No. 1,126,066 granted July 23, 1956.
Also, a number of commercially tried three-dimensional cinematography systems are described in detail in the April 1974 edition (Vol. 55, No. 4) of American Cinematographer magazine.
U.S. Pat. No. 2,135,049 to Harvey provides a system where a central reflector 24 rotates, or oscillates around the axis of the camera lens, and light from the scene is reflected by a rotating, or oscillating, secondary reflector 25. The angularity of the secondary reflector can be adjusted by the threaded rods 32, thus the reflectors can in a sense be focused upon some spot in a scene, but this adjustment can only be changed with the apparatus at rest, not dynamically. Also the motion of the secondary reflector is stated to be one revolution in thirty seconds (2 rev/min) or slower, for the ordinary cinema frame rate of twenty-four frames per second.
U.S. Pat. No. 2,101,979 to Brock discloses a system wherein sets of mirrors are amounted on a rotating disc or wheel BC', and rotated synchronously before the lens A' of a movie camera A. The optical result is described in the diagrams which comprise FIGS. 3, 4 and 5 of that patent.
U.S. Pat. No. 2,161,120 to Alder discloses a system in which a mirror 25 is carried and positioned by a damped armature piece, under the control of a set of electromagnet coils which are actuated according to the frame rate of the camera. U.S. Pat. No. 2,792,745 to Weber discloses a rotating mirror 3 with an aperture, driven in synchronism with the camera to reflect light into the camera lens. Behind the aperture a second mirror 16 provides a second light path to the lens. The space between the surfaces of these two mirrors determines the stereo separation or base, and is adjustable. Also the angularity of mirror 16 can be adjusted with respect to mirror 3, to adjust the stereo angle and thus adjust the point where the two light paths intersect, independently of the camera lens system.
U.S. Pat. No. 3,891,303 to Barquero considers the problem of binocular focusing, and suggests as a solution a system of reflectors which reverses side for side the scenes viewed by each eye, and uses visors fitted to the viewer to limit and direct his field of view.